Power MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) are examples of semiconductor devices which are used for switching power or energy sources, inverter devices or the like. By way of example, these MOSFETs are designed to switch high voltages in the case of low-impedance loads, such that there is a very small switching and conduction loss and thus a low area-specific on resistance Ron* A, where A denotes the area required for the power MOSFET. At the same time, a high breakdown voltage should be present in power MOSFETs in the switched-off state. Depending on the voltage class, a power MOSFET in the switched-off state withstands a drain-source voltage VDS of a few tens to a few hundreds of volts, for example 300 to 800 volts. Furthermore, power MOSFETs should conduct a very high current which can be up to a few hundred amperes at a gate-source voltage of approximately 10 to 20 V under a low voltage drop VDS.
In order to satisfy the increasing demands for a low Ron*A and a high breakdown voltage, it is desirable to develop new concepts for a semiconductor device, for example a vertical semiconductor device. Examples of such semiconductor devices are found in IP.COM-publication No. IPCOM000010537D (Jan. 23, 2003) “Trench DMOS für Kompensationsbauelemente” by O. Häberlen and M. Rüb (http://ip.com/IPCOM/000010537).